Do not clear references when the task_struct's mm is NULL by using
/proc/pid/clear_refs.
Also, use mmap_sem since the mm_struct's VMA's are being iterated in
fs/proc/task_mmu.c.
Reported by Oleg Nesterov <[email protected]>.
Signed-off-by: David Rientjes <[email protected]>
---
fs/proc/base.c | 9 ++++++++-
1 files changed, 8 insertions(+), 1 deletions(-)
diff --git a/fs/proc/base.c b/fs/proc/base.c
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -719,6 +719,7 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
struct task_struct *task;
+ struct mm_struct *mm;
char buffer[PROC_NUMBUF], *end;
memset(buffer, 0, sizeof(buffer));
@@ -733,7 +734,13 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
task = get_proc_task(file->f_path.dentry->d_inode);
if (!task)
return -ESRCH;
- clear_refs_smap(task->mm->mmap);
+ mm = get_task_mm(task);
+ if (mm) {
+ down_read(&mm->mmap_sem);
+ clear_refs_smap(mm->mmap);
+ up_read(&mm->mmap_sem);
+ mmput(mm);
+ }
put_task_struct(task);
if (end - buffer == 0)
return -EIO;
-
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